Friction linings of this type are used, in particular, for clutch disks of friction clutches in motor vehicles, a frictional lock between metallic friction surfaces of the friction clutch and the friction linings which, depending on the mode of operation of the friction clutch, can adhere or slip and transmits a corresponding torque from a drive unit to an output.
Owing to the high rotational speeds of the friction clutch, the friction lining is to have a high rotational bursting speed. In order to ensure long-term operation, the friction lining is to be wear-resistant and nevertheless have good coefficients of friction.
In order to increase the bursting strength of the friction lining, it is already known to deposit binder-impregnated strand material of friction-resistant materials, for example yarn, in a plurality of flat plies in a corrugated manner in the circumferential direction, the turns of the strand material being guided elliptically, for example, from outside diameter to outside diameter forming reversal regions and keeping the inside diameter free, the reversal regions from one turn to the other being offset in each case at an angle over the circumference. It is therefore possible to increase the portion of strand material in the overall composition of the friction lining and thus the friction and bursting strength of the latter. Winding usually takes place with the aid of a winding machine, one ply by definition being wound per revolution in the circumferential direction. The number of reversal regions on the external circumference of the friction lining is referred to as the winding ratio. By way of example, a winding ratio of 1:10 describes that the strand material has ten reversal regions on the external circumference over one circumference. Blanks wound in this manner are pressed to their final shape in a hot-pressing process. In order to obtain a stable and nondeformable friction lining which provides the required performance, the latter is designed in an empirically determined thickness which, in addition to the friction layer which diminishes as a result of wear during operation, includes a carrier layer which, in particular, may have another winding beneficial for the load-bearing capacity.
Particularly in the case of thin friction linings, the friction lining may become warped under the action of heat. Use is therefore made of metal carrier sheets which, after the friction part formed from the hot-pressed blank has been produced, are adhesively bonded to the carrier part in a plurality of process steps to form a friction lining.